did something

config.def.h

@@ -7,6 +7,9 @@
 static const int sloppyfocus               = 1;  /* focus follows mouse */
 static const int bypass_surface_visibility = 0;  /* 1 means idle inhibitors will disable idle tracking even if it's surface isn't visible  */
 static const int smartborders              = 1;
+static const int smartgaps                 = 0;  /* 1 means no outer gap when there is only one window */
+static int gaps                            = 1;  /* 1 means gaps between windows are added */
+static const unsigned int gappx            = 10; /* gap pixel between windows */
 static const unsigned int borderpx         = 1;  /* border pixel of windows */
 static const float rootcolor[]             = COLOR(0x222222ff);
 static const float bordercolor[]           = COLOR(0x444444ff);
@@ -147,6 +150,7 @@ static const Key keys[] = {
 	{ MODKEY,                    XKB_KEY_l,          setmfact,       {.f = +0.05f} },
 	{ MODKEY,                    XKB_KEY_Return,     zoom,           {0} },
 	{ MODKEY,                    XKB_KEY_Tab,        view,           {0} },
+	{ MODKEY,                    XKB_KEY_g,          togglegaps,     {0} },
 	{ MODKEY|WLR_MODIFIER_SHIFT, XKB_KEY_C,          killclient,     {0} },
 	{ MODKEY,                    XKB_KEY_t,          setlayout,      {.v = &layouts[0]} },
 	{ MODKEY,                    XKB_KEY_f,          setlayout,      {.v = &layouts[1]} },

config.h

@@ -9,6 +9,9 @@
 static const int sloppyfocus               = 1;  /* focus follows mouse */
 static const int bypass_surface_visibility = 0;  /* 1 means idle inhibitors will disable idle tracking even if it's surface isn't visible  */
 static const int smartborders              = 1;
+static const int smartgaps                 = 1;  /* 1 means no outer gap when there is only one window */
+static int gaps                            = 1;  /* 1 means gaps between windows are added */
+static const unsigned int gappx            = 5; /* gap pixel between windows */
 static const unsigned int borderpx         = 1;  /* border pixel of windows */
 static const float rootcolor[]             = COLOR(0x222222ff);
 static const float bordercolor[]           = COLOR(0x444444ff);

dwl.c

@@ -214,6 +214,7 @@ struct Monitor {
 	struct wl_list layers[4]; /* LayerSurface.link */
 	const Layout *lt[2];
 	Pertag *pertag;
+	int gaps;
 	unsigned int seltags;
 	unsigned int sellt;
 	uint32_t tagset[2];
@@ -364,6 +365,7 @@ static void toggledimmingclient(const Arg *arg);
 static void togglefloating(const Arg *arg);
 static void togglesticky(const Arg *arg);
 static void togglefullscreen(const Arg *arg);
+static void togglegaps(const Arg *arg);
 static void toggletag(const Arg *arg);
 static void toggleview(const Arg *arg);
 static void unlocksession(struct wl_listener *listener, void *data);
@@ -1094,6 +1096,8 @@ createmon(struct wl_listener *listener, void *data)
 
 	wlr_output_state_init(&state);
 	/* Initialize monitor state using configured rules */
+	m->gaps = gaps;
+
 	m->tagset[0] = m->tagset[1] = 1;
 	for (r = monrules; r < END(monrules); r++) {
 		if (!r->name || strstr(wlr_output->name, r->name)) {
@@ -2979,7 +2983,7 @@ tagmon(const Arg *arg)
 void
 tile(Monitor *m)
 {
-	unsigned int mw, my, ty, draw_borders = 1;
+	unsigned int h, r, e = m->gaps, mw, my, ty, draw_borders = 1;
 	int i, n = 0;
 	Client *c;
 
@@ -2988,26 +2992,33 @@ tile(Monitor *m)
 			n++;
 	if (n == 0)
 		return;
+	if (smartgaps == n)
+		e = 0;
 
 	if (n == smartborders)
 		draw_borders = 0;
 
 	if (n > m->nmaster)
-		mw = m->nmaster ? (int)roundf(m->w.width * m->mfact) : 0;
+		mw = m->nmaster ? (int)roundf((m->w.width + gappx*e) * m->mfact) : 0;
 	else
 		mw = m->w.width;
-	i = my = ty = 0;
+	i = 0;
+	my = ty = gappx*e;
 	wl_list_for_each(c, &clients, link) {
 		if (!VISIBLEON(c, m) || c->isfloating || c->isfullscreen)
 			continue;
 		if (i < m->nmaster) {
-			resize(c, (struct wlr_box){.x = m->w.x, .y = m->w.y + my, .width = mw,
+			r = MIN(n, m->nmaster) - i;
-				.height = (m->w.height - my) / (MIN(n, m->nmaster) - i)}, 0, draw_borders);
+			h = (m->w.height - my - gappx*e - gappx*e * (r - 1)) / r;
-			my += c->geom.height;
+			resize(c, (struct wlr_box){.x = m->w.x + gappx*e, .y = m->w.y + my,
+				.width = mw - 2*gappx*e, .height = h}, 0, 1);
+			my += c->geom.height + gappx*e;
 		} else {
+			r = n - i;
+			h = (m->w.height - ty - gappx*e - gappx*e * (r - 1)) / r;
 			resize(c, (struct wlr_box){.x = m->w.x + mw, .y = m->w.y + ty,
-				.width = m->w.width - mw, .height = (m->w.height - ty) / (n - i)}, 0, draw_borders);
+				.width = m->w.width - mw - gappx*e, .height = h}, 0, 1);
-			ty += c->geom.height;
+			ty += c->geom.height + gappx*e;
 		}
 		i++;
 	}
@@ -3061,6 +3072,13 @@ togglesticky(const Arg *arg)
 	setsticky(c, !c->issticky);
 }
 
+void
+togglegaps(const Arg *arg)
+{
+	selmon->gaps = !selmon->gaps;
+	arrange(selmon);
+}
+
 void
 toggletag(const Arg *arg)
 {